EV Technology Today-Batteries
We’ve truly entered the EV age and even though most of us will still go for the conventional Petrol or Diesel car if we were to buy a new car today, we know in the back of our minds that soon we would opt for the EV instead in the foreseeable future. Most believe that by 2025 Electric cars will almost totally replace conventional internal combustion engine cars as the first buying choice.
I spoke about the brief history and the current status of EVs in the last newsletter of 20th May 2022. If you would like to refer to the post it is here.
Moving on, let us say the key parts of the EV are a) Battery, b) Motor. Today we are talking about the battery and in the next issue we shall talk about the motor. After that we will take up an issue on the chargers.
If you look at the battery picture above, which happens to be a Panasonic battery manufactured for Tesla, you will notice that it is made up of small cells like the one shown below:
A battery pack has several battery modules. Each battery module has many cells, typically 450 cells for the Tesla model 3. Each module typically generates 24V DC output. On the top and bottom side of the module we have metal contacts to electrically connect each individual cell. More importantly, running as a zig zag around each and every cell is cooling jacket through which a coolant flows and is cooled via a pump and radiator at the front side. Cooling is very essential as the battery current can be very high during acceleration, braking and charging. These batteries are predominantly Lithium-Ion types. In the lithium-ion batteries, the negative electrode is made of graphite, a form of carbon, the positive electrode is made of a metal oxide, such as lithium cobalt oxide, and the electrolyte is a lithium salt dissolved in an organic solvent. The movement of lithium ions between the electrodes creates the energy of the battery. The other important component of the battery modules is the electronic battery management circuit which always monitors and controls the health of the battery.
The current day life of a battery pack is 100,000 to 200,000 hours. After a battery pack is retired from an EV, it can be put to use for other, less demanding applications like homes, shops, offices, grid power storage, amongst others.
The Tesla model 3 battery pack has a capacity of 82KWh. This battery gives it a range of 500Kms, and it can be charged within 10 hours using the on-board 240V charger.
The electric car typical layout for key components is given below. As you will notice the battery pack, being one of the heaviest components of the EV is placed at the bottom below the floor of the car. This helps in keeping the center of gravity as low as possible, thereby contributing to the stability and grip of the EV to the road.
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